sdbusplus: use shorter type aliases

The sdbusplus headers provide shortened aliases for many types.
Switch to using them to provide better code clarity and shorter
lines.  Possible replacements are for:
  * bus_t
  * exception_t
  * manager_t
  * match_t
  * message_t
  * object_t
  * slot_t

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I6a559082fed34ae62b648345ead793436d2d03f6
diff --git a/src/watch.hpp b/src/watch.hpp
index c206316..5cf2c19 100644
--- a/src/watch.hpp
+++ b/src/watch.hpp
@@ -39,8 +39,7 @@
     virtual void callback(Context ctx) = 0;
 
     /** @brief Invoke the callback associated with the watch. */
-    virtual void callback(Context /* ctx */,
-                          sdbusplus::message::message& /* msg */){};
+    virtual void callback(Context /* ctx */, sdbusplus::message_t& /* msg */){};
 };
 
 } // namespace monitoring